docs: def _process_pub2pubmed(self, limit=None):
          """
          This will pull the zfin internal publication to pubmed mappings.
          Somewhat redundant with the process_pubinfo method,
          but this includes additional mappings.
  
          <pub_id> is an individual
          <pub_id> rdfs:label <pub_label>
          <pubmed_id> is an individual
          <pubmed_id> rdfs:label <pub_label>
  
          <pub_id> sameIndividual <pubmed_id>
          :param limit:
          :return:
          """
          line_counter = 0
          if self.test_mode:
              graph = self.testgraph
          else:
              graph = self.graph
          model = Model(graph)
          raw = '/'.join((self.rawdir, self.files['pub2pubmed']['file']))
          with open(raw, 'r', encoding="latin-1") as csvfile:
              filereader = csv.reader(csvfile, delimiter='\t', quotechar='\"')
              for row in filereader:
                  line_counter += 1
                  (pub_id, pubmed_id
                   # , empty
                  ) = row
  
                  if self.test_mode and (
                          'ZFIN:' + pub_id not in self.test_ids['pub'] and
                          'PMID:' + pubmed_id not in self.test_ids['pub']):
                      continue
  
                  pub_id = 'ZFIN:' + pub_id.strip()
                  rtype = None
                  if pubmed_id != '' and pubmed_id is not None:
                      pubmed_id = 'PMID:' + pubmed_id.strip()
                      rtype = self.globaltt['journal article']
                      rpm = Reference(graph, pubmed_id, rtype)
                      rpm.addRefToGraph()
                      model.addSameIndividual(pub_id, pubmed_id)
                  ref = Reference(graph, pub_id, rtype)
                  ref.addRefToGraph()
                  if not self.test_mode and limit is not None and line_counter > limit:
                      break
  
          return